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Neomycin
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Neomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments and eyedrops.
ycin is overwhelmingly used as a topical preparation, such as Neosporin. It can also be given orally, where it is usually combined with other antibiotics. Neomycin is not absorbed from the gastrointestinal tract, and has been used as a preventative measure for hepatic encephalopathy and hypercholesterolemia.
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Encyclopedia
Neomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments and eyedrops.
Uses
Neomycin is overwhelmingly used as a topical preparation, such as Neosporin. It can also be given orally, where it is usually combined with other antibiotics. Neomycin is not absorbed from the gastrointestinal tract, and has been used as a preventative measure for hepatic encephalopathy and hypercholesterolemia. By killing bacteria in the intestinal tract, it keeps ammonia levels low and prevents hepatic encephalopathy, especially prior to GI surgery. It has also been used to treat small intestinal bacterial overgrowth. It is not given intravenously, as neomycin is extremely nephrotoxic (causes kidney damage), especially compared to other aminoglycosides. The exception is when neomycin is included, in very small quantities, as a preservative in some vaccines - typically 0.025 mg per dose.
Molecular Biology
Neomycin resistance is conferred by either one of two aminoglycoside phosphotransferase genes. A neo gene is commonly included in DNA plasmids used by molecular biologists to establish stable mammalian cell lines expressing cloned proteins in culture; many commercially available protein expression plasmids contain neo as a selectable marker. Non-transfected cells will eventually die off when the culture is treated with neomycin or similar antibiotic. Neomycin or kanamycin can be used for prokaryotes, but geneticin (G418) is generally needed for eukaryotes.
Spectrum
Similar to other aminoglycosides, neomycin has excellent activity against Gram negative bacteria, and has partial activity against Gram positive bacteria. It is relatively toxic to humans, and many people have allergic reactions to it. See: Hypersensitivity. Physicians sometimes recommend using antibiotic ointments without neomycin, such as Polysporin.
History
Neomycin was discovered in 1949 by the microbiologist Selman Waksman and his student Hubert Lechevalier at Rutgers University. It is produced naturally by the bacterium Streptomyces fradiae.
Neomycin as a DNA binder
Neomycin belongs to the family of aminoglycosides. This family is comprised of many other medicinally important drugs: streptomycin, saromomycin and kanamycin to name just a few. Aminoglycosides are proverbially known for their ability to bind to duplex RNA with high affinity. In a study done by Pilch and coworkers, the association constant for neomycin with A-site RNA was found to be in the ~109 range. However more than 50 years after its discovery, its DNA binding properties were still unknown. In 2000, Arya and coworkers discovered that neomycin induces enormous thermal stabilization of triplex DNA while having little or almost no effect on the DNA duplex stabilization. They also showed that, neomycin likes anything that adopts A-form type structure, triplex DNA being one of them. They later went on to show that neomycin even induces DNA:RNA hybrid triplex formation. Their continuous search for selective ligands for a particular type of nucleic acid gave rise to many new conjugates. Neomycin-BQQ when they tried to combined the best in triplex recognition, Neomycin-Hoechst 33258 conjugate for targeting B-DNA (neomycin alone doesn't bind to a typical duplex B-DNA) and Neomycin Methidium conjugate for targeting DNA:RNA hybrids.
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